af       d                          eb     c  gh
[..............yyyyyyyy....................][......xxxxxxxyyy........................]

              af        d                          eb     c gh
[..............yyyyyyyyy...................][.......xxxxxxxyy........................]

              af         d                          eb     cgh
[..............yyyyyyyyyy..................][........xxxxxxxy........................]

              af         gd                          eb     ch
[..............yyyyyyyyyyy.................][.........xxxxxxx........................]